Blocking and superconditioning procedures will be used to evaluate two general types of theories about transfer from appetitive to aversive conditioning. These theories emphasize either the "affective-value" or the "signal-value" of a conditioned stimulus (CS). Many affective value theories include a reciprocal inhibition hypothesis, which specifies that an excitor for one motivational system (aversive or appetitive) is functionally equivalent to an inhibitor for the other system. Affective-value predictions are therefore that aversive conditioned excitors (AvCS plus s) function as appetitive conditioned inhibitors (ApCS minus s), and that AvCS minus s and ApCS plus s also function equivalently. Signal-value theory predictions assume functional equivalence of all CS plus s and of all CS minus s, irrespective of their motivational significance. Rats will initially receive aversive conditioning. During aversive to appetitive transfer, one or more elements of the ApCS plus will be a former AvCS plus or AvCS minus. Appetitive conditioning will be indexed by behavior directed toward the food-delivery tray (goal-tracking) during the ApCS plus, and will continue until goal-tracking is asymptotic. When the ApCS plus is a compound, blocking and superconditioning will be assayed by testing its elements for control of goal-tracking. Blocking is conditioning less than normal excitation to one element of a compound excitatory CS as a result of another element's prior excitatory relationship to the signalled event (US). Superconditioning is conditioning greater than normal excitation to one element of a compound excitatory CS as a result of another element's prior inhibitory relationship to the US. In the proposed experiments, the US is changed from aversive to appetitive at the outset of appetitive conditioning, and predictions of blocking and superconditioning are derived from the two types of theories.